1. Field of Invention
This invention relates to a gearing with a split gear having two toothed portions.
2. Description of Prior Art
In symmetrical double helical or herringbone type gears, tooth meshing errors cause uneven distribution of applied loads between two toothed portions of the symmetrical double helical or herringbone type gear.
Accordingly, efforts have been made when designing double toothed helical gears to eliminate or at least to reduce tooth meshing errors. For example, U.S. Pat. No. 3,102,433 to Stoeckict discloses a gear mechanism wherein one gear is axially fixed. The other gear moves axially along its shaft or axially together with its shaft. Each gear is comprised of two toothed portions. The teeth of the first toothed portion have an inclination angle in one direction and a normal pressure angle. The teeth of the second toothed portion have an inclination angle in the opposite direction and have a normal pressure angle. The inclination angle of the teeth of the second toothed portion is greater than the inclination angle of the first toothed portion. The normal pressure angle of the second toothed portion is smaller than the normal pressure angle of the first toothed portion. A substantially greater portion of an applied load is taken-up permanently by the toothed portion having the lesser inclination angle. The gearing is less sensitive to the variations of load- distribution due to the mesh errors than is a gearing of the symmetrical herringbone type.
Symmetrical herringbone type gearings have toothed portions which are fixed to each other, however, symmetrical herringbone type gearings exhibit the following disadvantages:
(a) Effective face width of the symmetrical herringbone type gearings is the same as a typical gearing. For increasing loading ability there is a need to increase a center distance. The weight of the gear assembly will increase too.
(b) The technological process for manufacture of the teeth of the gears is expensive.
(c) Presence of a dynamic load on the gear teeth, particularly for high-speed gearing.
Further, for high-speed gearings unavoidable inaccuracies in the tooth mesh due to the tolerance, as well as errors in manufacturing and assembly, lead to high-frequency periodic accelerations of the driven gear. These accelerations result in the imposition of acceleration forces on the meshing teeth. Due to the presence of backlash between non-working tooth flanks, the acceleration of the driven gear leads also to separation of the working teeth followed by a reengagement. As a result, impact load is imposed on the gear teeth. This phenomenon, known as free impact or hammering, results in high dynamic loading on the gear teeth with attendant noise generation and vibration occurring.
An example of anti-backlash gearings are presented in U.S. Pat. No. 4,612,816 to Chalik. Each gear has coaxially disposed first and second toothed portions. The teeth of the first toothed portion have a first inclination angle. The teeth of the second toothed portion have a second inclination angle different from the first inclination angle. One of the meshing gears is fixed to its shaft, while the other is mounted so as to be axially displaceable with respect to the fixed gear. Preloading means urge the floating gear against the fixed gear. The teeth of the first toothed portion of the floating gear mesh with the teeth of the first toothed portion of the fixed gear. The teeth of the second toothed portions of the floating gear mesh with the teeth of the second toothed portion of the floating gear along the opposite tooth flanks with respect to each other.
The gear assembly taught by Chalik exhibits the following disadvantages:
(a) Preloading means have a large, complex, and complex adjustment.
(b) The gear assembly can be used only in non-reversible one stage gear set.
(c) Manufacturing of the gear assembly is expensive.
Basic objects and advantages of the present invention may comprise the following:
(a) to provide even distribution of an applied load between the floating toothed portions for increasing the loading ability of the gearing without increasing the center distance. The weight of the gear assembly will increase insignificantly. Service life will stay the same.
(b) to provide smooth working of the gearing.
(c) to eliminate dynamic load on the gear teeth for high-speed reversible gearing without the use of toothed portions with different helix angles and the means for preloading.
The objects and advantages may enable the use of the invention for gearing of any classification and in a reversible multi-stage gear assembly.
Additional features and advantages of the present invention are described in, and will be apparent from, the detailed description of the presently preferred embodiments and from the drawings.